Desk top computers are being used more and more often to perform plural applications concurrently. For example, a user can concurrently access and utilize a spreadsheet application program and a word processing application program.
Each application program can communicate with the user in a variety of ways. This is referred to as multimedia and includes visually displaying data, text, graphics or video, and providing an audio response. An application program speaks to a user by providing an audio response to an audio output device, such as a speaker. The audio response can be simple, taking the form of tones or beeps, or it can be more complex, mimicking human speech. An example of a complex audio response is a text-to-speech operation where speech is digitally synthesized.
Application programs providing audio responses are designed under the assumption that only one application program at a time will speak to a user. Therefore, problems arise when a user concurrently uses two or more application programs that provide audio responses. When two or more programs are running on a computer at the same time, the user may be unable to identify which particular application program is speaking at any given time, because the application programs do not identify themselves. Another problem arises if two or more of the application programs speak at the same time. The user can be easily confused and may be unable to understand what was said. Worse yet, the application programs could speak and their combined message produce an unintended result. For example, a first application program could say "erase", followed by a second application program saying ". . . all files". Each application program masks part of the other application program's message. The resulting message "erase all files" could erroneously cause the user to erase all of his files.